AP Physics 1 2018 Free Response Solutions

The paragraph discusses the analysis of a spacecraft moving in a clockwise circular orbit around the Earth. The focus is on identifying the forces acting on the spacecraft, which is primarily the gravitational force. The speaker then attempts to derive an equation for the orbital period in terms of the spacecraft's mass, Earth's mass, radius, and physical constants. This derivation is based on the concept of centripetal force and leads to an equation that resembles Kepler's third law. The discussion also covers the impact of introducing a second spacecraft of mass 2m into the same orbit and explains why the orbital period remains unchanged. Lastly, the paragraph explores the change in speed of the first spacecraft when it moves into a new orbit with a larger radius, concluding that the speed decreases as the radius increases.

This paragraph delves into an experiment involving conductive dough, which is molded into cylinders and tested for resistance. The goal is to determine the resistivity of the material. The speaker outlines the process of plotting resistance against the cross-sectional area and length of the cylinders to derive the resistivity. The paragraph also addresses the second part of the question, which asks about the impact of shaping the dough into rectangular forms instead of cylinders. The speaker clarifies that resistivity is a material property and does not depend on the shape of the dough. The paragraph concludes with a proposed experimental procedure to determine the effect of temperature on the resistivity of the dough cylinders, suggesting a method that involves heating the dough and measuring changes in resistance.

The paragraph focuses on the analysis of angular acceleration and rotational inertia using graphical methods. The scenario involves a disc spinning around an axle, where friction between the axle and the disc exerts a constant torque. The speaker explains how to graph the disc's angular acceleration over time and derive the rotational inertia from the slope of the graph. The paragraph also discusses how the torque would change when oil is applied to reduce friction, altering the graph's shape. The speaker then selects the best mathematical model to represent the torque based on the given options and explains the rationale behind the choice.

This paragraph examines the motion of a transverse wave traveling along a string, with specific attention given to two points, P and Q. The speaker describes how to determine the instantaneous velocity and acceleration of a point on the wave at a given moment. A graphical representation is used to illustrate the position of the wave at a later time, with the speaker providing a step-by-step explanation of how to plot the wave's new position. The paragraph concludes with an analysis of the total distance traveled by point P over one full period of the wave, emphasizing the importance of units in calculations.

The final paragraph of the script discusses a spring-block oscillator system, where a second block with twice the mass of the original is added to the system. The speaker calculates the new period and amplitude of oscillation, comparing them to the original values. The explanation involves the application of conservation of energy and momentum principles. The speaker concludes that the new amplitude will be less than the original due to the decrease in maximum kinetic energy, which in turn affects the spring's potential energy at maximum amplitude. The paragraph ends with a reflection on the overall difficulty and reasonableness of the 2018 AP Physics free response test.